Aim : The purpose of this in vitro study was to compare the marginal gap discrepancy of lithium disilicate single crown fabricated with computer-aided design and computer-aided manufacturing (CAD/CAM) technology by using both conventional and digital impression techniques Materials & Methods: Lithium disilicate crowns were fabricated to fit on metal die either by digital impressions with Cerec 3D omnicam, followed by milling from IPS e.max CAD and conventional impression followed by fabrication of IPS e.max Press by using the lost-wax and heat-pressing techniques. Each crown was fixed to metal die and the marginal gap was measured for each specimen at 3 points under magnification with a stereomicroscope. Data were statistically analyzed by T test. Results: The all ceramic specimens fabricated by digital image had a mean marginal adaptation width 79.9 μm buccally and 77.1 μm lingually, and the all ceramic specimens fabricated by conventional impression had a mean marginal adaptation width 84.6 μm buccally and 84.4 μm lingually with a significant difference. CONCLUSION: Within the limitations of this study, all-ceramic crowns produced by CAD/ CAM system had external marginal adaptation accuracy better than all-ceramic crowns produced by dental laboratory with statistical significant difference